1. Field of the Invention
This invention relates to a method of moving a molten zone of material through a solid body of semiconductor material and, in particular, to the migration of a metal "wire" through material, having a diamond cubic crystal structure and at least one surface of the body has a (100) planar orientation.
2. Description of the Prior Art
W. G. Pfann describes in "Zone Melting", John Wiley and Sons, Inc., New York (1966), a thermal gradient zone melting process to produce various desirable material configurations in a body of semiconductor material. The process had previously been disclosed in his issued U.S. Pat. No. 2,813,048, based on his application filed June 24, 1954. In both instances, cavities are generally formed in the surface of the body and a piece of wire of the metal to be migrated is disposed in the cavity. However, the resulting structures were not desirable for semiconductor usage.
M. Blumenfeld, in U.S. Pat. No. 3,897,277, teaches alloying aluminum to the surface of a body of silicon semiconductor material in an attempt to maintain the registry of the pattern of metal deposits to be migrated. However, problems of registry of the metal still plague one's attempt to obtain the precise orientation necessary for an array of deep diodes suitable for making X-ray imaging devices.
Recently, T. R. Anthony and H. E. Cline, discovered that employing selected etching of the surface and preferred crystallographic orientation enabled one to employ thermal gradient zone melting processing to make semiconductor devices commercially. The improved process resulted in a large savings in energy required to process semiconductor materials and increased the yields of devices fabricated thereby. For further information, one is directed to the teachings of Anthony and Cline in their recently granted U.S. Pat. No. 3,904,442, and co-pending patent application Ser. No. 519,913.
A wafer thickness of from 6 mils to 10 mils or more is most often employed because of handling problems encountered in semiconductor processing. The requirement of etching grooves to deposit metal therein for subsequent migration may lead to wafer breakage if personnel abuse the wafers in their handling required during processing. Additionally, it is desirable to minimize the required processing steps of the wafers since each step enhances the chance of some undesirable happening occurring to the wafer as it is processed.
In a co-pending application, Ser. No. 634,247 filed Nov. 21, 1975; Chang, Cline and Anthony, describe a method of using an oxide mask to initiate the migration process. Elimination of this step is also desirable, if practical, should it have the ability to be reproducible on a commercial scale.
It is therefore an object of this invention to provide a new and improved method for moving a molten zone within a solid body, or wafer, of semiconductor material which overcomes the deficiencies of the prior art.
Another object of this invention is to provide a new and improved method of migrating a molten zone of a metal-rich semiconductor material through a solid body or wafer, of semiconductor material without the use of etched grooves and/or oxide masking on the surface of the wafer or body.
Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter.